Dear Frodo (or Jedi) The results seems to confirm your assumption that 3 systems are different. How you should present results probably depends on how it is usual to report such results in your environment.
BTW. It seems to me like homework and this list has no homework policy (Sorry, if I am mistaken). Cheers Petr > -----Original Message----- > From: R-help <r-help-boun...@r-project.org> On Behalf Of Frodo Jedi > Sent: Monday, November 12, 2018 2:08 AM > To: r-help@r-project.org > Subject: [R] Reporting binomial logistic regression from R results > > Dear list members, > I need some help in understanding whether I am doing correctly a binomial > logistic regression and whether I am interpreting the results in the correct > way. > Also I would need an advice regarding the reporting of the results from the R > functions. > > I want to report the results of a binomial logistic regression where I want to > assess difference between the 3 levels of a factor (called System) on the > dependent variable (called Response) taking two values, 0 and 1. My goal is to > understand if the effect of the 3 systems (A,B,C) in System affect differently > Response in a significant way. I am basing my analysis on this URL: > https://stats.idre.ucla.edu/r/dae/logit-regression/ > > This is the result of my analysis: > > > fit <- glm(Response ~ System, data = scrd, family = "binomial") > > summary(fit) > > Call: > glm(formula = Response ~ System, family = "binomial", data = scrd) > > Deviance Residuals: > Min 1Q Median 3Q Max > -2.8840 0.1775 0.2712 0.2712 0.5008 > > Coefficients: > Estimate Std. Error z value Pr(>|z|) > (Intercept) 3.2844 0.2825 11.626 < 2e-16 *** > SystemB -1.2715 0.3379 -3.763 0.000168 *** > SystemC 0.8588 0.4990 1.721 0.085266 . > --- > Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 > > (Dispersion parameter for binomial family taken to be 1) > > Null deviance: 411.26 on 1023 degrees of freedom Residual deviance: > 376.76 on 1021 degrees of freedom > AIC: 382.76 > > Number of Fisher Scoring iterations: 6 > Following this analysis I perform the wald test in order to understand whether > there is an overall effect of System: > > library(aod) > > > wald.test(b = coef(fit), Sigma = vcov(fit), Terms = 1:3) > Wald test: > ---------- > > Chi-squared test: > X2 = 354.6, df = 3, P(> X2) = 0.0 > The chi-squared test statistic of 354.6, with 3 degrees of freedom is > associated > with a p-value < 0.001 indicating that the overall effect of System is > statistically > significant. > > Now I check whether there are differences between the coefficients using again > the wald test: > > # Here difference between system B and C: > > > l <- cbind(0, 1, -1) > > wald.test(b = coef(fit), Sigma = vcov(fit), L = l) > Wald test: > ---------- > > Chi-squared test: > X2 = 22.3, df = 1, P(> X2) = 2.3e-06 > > > > # Here difference between system A and C: > > > l <- cbind(1, 0, -1) > > wald.test(b = coef(fit), Sigma = vcov(fit), L = l) > Wald test: > ---------- > > Chi-squared test: > X2 = 12.0, df = 1, P(> X2) = 0.00052 > > > > # Here difference between system A and B: > > > l <- cbind(1, -1, 0) > > wald.test(b = coef(fit), Sigma = vcov(fit), L = l) > Wald test: > ---------- > > Chi-squared test: > X2 = 58.7, df = 1, P(> X2) = 1.8e-14 > > My understanding is that from this analysis I can state that the three systems > lead to a significantly different Response. Am I right? If so, how should I > report > the results of this analysis? What is the correct way? > > > Thanks in advance > > Best wishes > > FJ > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. Osobní údaje: Informace o zpracování a ochraně osobních údajů obchodních partnerů PRECHEZA a.s. jsou zveřejněny na: https://www.precheza.cz/zasady-ochrany-osobnich-udaju/ | Information about processing and protection of business partner’s personal data are available on website: https://www.precheza.cz/en/personal-data-protection-principles/ Důvěrnost: Tento e-mail a jakékoliv k němu připojené dokumenty jsou důvěrné a podléhají tomuto právně závaznému prohláąení o vyloučení odpovědnosti: https://www.precheza.cz/01-dovetek/ | This email and any documents attached to it may be confidential and are subject to the legally binding disclaimer: https://www.precheza.cz/en/01-disclaimer/ ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
